Headrest for a bathtub



FIG. 1 is a perspective view of a headrest for a bathtub;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a right side elevation view thereof, the left side being a mirror image thereof;

FIG. 5 is a bottom plan view thereof; and,

FIG. 6 is a rear elevation view thereof. 

The ornamental design for a headrest for a bathtub, as shown and described. 